Powerhead of a power injection system

ABSTRACT

A contrast media injection system includes detects the absolute position of the syringe ram using a non-contact sensor. A series of magnets and Hall-Effect sensors may be used or an opto-reflective system. Illuminated knobs that are connected to the drive mechanism for the syringe ram rotate with the drive and provide visual feedback on operation through the illumination. Analog Hall-Effect sensors are used to determine the presence or absence of magnets that identify the type of faceplate being used. The faceplates include control electronics, connected to the powerhead through connectors, which may be interchangeably used by the two faceplates. The faceplate electronics include detectors for automatically detecting the capacity of pre-filled syringes. Additional features include using historical data to provide optimum pressure limit values during an injection protocol, a removable memory device for storing and transferring information such as injection protocols and injector statistics, and password protection of such protocols.

CROSS REFERENCE TO RELATED APPLICATION

The present application is related to co-pending and concurrently filedapplication Ser. No. ______, entitled IMPROVEMENTS TO POWERHEAD CONTROLIN A POWER INJECTION SYSTEM, which is hereby incorporated by referenceherein in its entirety.

FIELD OF THE INVENTION

The present invention relates to contrast media injector systems and,more particularly to improvements thereto.

BACKGROUND OF THE INVENTION

In many medical environments, a medical fluid is injected into a patientduring diagnosis or treatment. One example is the injection of contrastmedia into a patient to improve CT, Angiographic, Magnetic Resonance orUltrasound imaging, using a powered, automatic injector.

Injectors suitable for these and similar applications typically must usea relatively large volume syringe and be capable of producing relativelylarge flow rates and injection pressures. For this reason, injectors forsuch applications are typically motorized, and include a large, highmass injector motor and drive train. For ease of use, the motor anddrive train are typically housed in an injection head, which issupported by a floor, wall, or ceiling mounted arm.

The injection head is typically mounted on the arm in a pivotal manner,so that the head may be tilted upward (with the syringe tip above theremainder of the syringe) to facilitate filling the syringe with fluid,and downward (with the syringe tip below the remainder of the syringe)for injection. Tilting the head in this manner facilitates removal ofair from the syringe during filling, and reduces the likelihood that airwill be injected into the subject during the injection process.Nevertheless, the potential for accidentally injecting air into apatient remains a serious safety concern.

In addition to the injection head discussed above, many injectorsinclude a separate console for controlling the injector. The consoletypically includes programmable circuitry which can be used forautomatic, programmed control of the injector, so that the operation ofthe injector can be made predictable and potentially synchronized withoperations of other equipment such as scanners or imaging equipment.

Thus, at least part of the injection process is typically automaticallycontrolled; however, the filling procedure, and typically some part ofthe injection procedure, are normally performed by an operator, usinghand-operated movement controls on the injector head. Typically, thehand-operated movement controls include buttons for reverse and forwardmovement of the injector drive ram, to respectively fill and empty thesyringe. In some cases, a combination of buttons is used to initiatemovement of the ram or to control ram movement speed. The injector headalso typically includes a gauge or display for indicating injectionparameters to the operator, such as the syringe volume remaining, forthe operator's use when controlling the injector head. Unfortunately,operators have found it cumbersome to use the hand-operated movementbuttons and to read the injector head gauges and displays, for severalreasons, not the least of which is the necessary tilting of the injectorhead between the upward, filling position to the downward, injectionposition, changing the positions of the hand-operated movement buttonsrelative to the operator, and at some tilt angles rendering the gaugesor displays difficult to read.

In many applications, it is desirable to use an injector with multipledifferent syringe sizes. For example, it may be desirable to use asmaller syringe for pediatric use than for adult use, or where aparticular procedure requires a smaller volume of fluid. To facilitatethe use of different syringe sizes, injectors have been constructed withremovable faceplates, where each of the various faceplates is configuredfor a particular syringe size. Typically, the injector is able to adjustinjection parameters by detecting which faceplate is mounted to theinjector, for example using a magnetic detector mounted to the frontsurface of the injector housing to detect the presence or absence of amagnet in the faceplate. Unfortunately, the necessity of incorporating amagnetic detector into the outer housing of the injector head increasesthe complexity and expense of manufacturing the injector head.

Recently, one development in power injectors has been the introductionof dual headed injectors, that is, an injector with two drive systemsand mountings for two syringes. The software for the injector providesfor independent control of these drive systems using both manualcontrols and programmed injection routines in response to a storedsequence. Such dual headed injectors allow multiple fluids to beinjected during a sequence without changing a syringe or otherequipment.

Regardless of the benefits of current power injector systems, whethersingle head or dual head, improvements and advances in this fieldcontinue to be desirable goals and will ensure that such equipmentbecomes easier to use, increase in functionality, and become morereliable and efficient in operation.

SUMMARY OF THE INVENTION

Accordingly embodiments of the present invention relate to improvingpower injectors that are used to inject contrast media and other fluidsin a patient or animal.

One aspect of the present invention relates to determining an absoluteposition of a syringe ram, without requiring contact between theposition sensor and the drive mechanism of the syringe ram. Inparticular, a series of Hall-Effect sensors are arranged along a paththat the syringe ram travels, and a magnet is coupled to a portion ofthe syringe ram. In any position of the syringe ram, the sensors candetect the magnet and based on which sensors are detecting the magnet,the position of the syringe ram can be determined.

In a specific embodiment of this aspect, analog Hall-Effect sensors areutilized, enabling increased accuracy in determining the position of themagnet relative to the sensors.

A second aspect of the present invention is similar except that it usesan optical sensor. In accordance with this aspect, a fixed opticalsensor transmits radiation to a reflective surface that is attached to amoving portion of the syringe ram. The strength of the reflected signalat the optical sensor is indicative of the distance from the sensor tothe reflective surface. Accordingly, a position of the syringe ram canbe determined based on the reflected signal.

Another aspect of the present invention relates to a manual control knobthat is operatively coupled with the mechanism that moves the syringeram. Because of this operative coupling, the knob rotates when thesyringe ram is moving under programmed control. Also, the knob rotatesat a speed that is directly indicative of the relative speed of thesyringe ram. The knob is advantageously illuminated such that itsrotation and speed of rotation is easily discernible. Accordingly, thecontrol knob movement provides direct feedback about the operation ofthe syringe ram. In disclosed embodiments, this feedback is enhanced bychanging the color of illumination of the knob to reflect the operativemode of the injector.

Yet another aspect of the present invention relates to using analogHall-Effect sensors to determine what type of faceplate is attached toan injector powerhead. Instead of relying on fixed-threshold digitalHall-Effect sensors, the analog sensors are used to calibrate athreshold value for each different faceplate. The calibrated thresholdscan, therefore, accommodate variations in manufacturing tolerances andmagnet strength. For each sensor, a signal level is determined with thefaceplate attached and the faceplate detached. The threshold value isset between those two signal levels. In disclosed embodiments, to permita wider range of magnet combinations and thereby accommodate morefaceplates, the Hall-effect sensors may be sensitive to polarity of themagnet, so that the North-South orientation of the magnets in thefaceplate may be included in the properties detected by the Hall-effectsensor to identify a faceplate.

Still another aspect of the present invention relates to safely settinga pressure limit value for a protocol that prevents excessive pressuresfrom occurring. In accordance with this aspect, historical data isacquired for a protocol when in it executed. The historical data canindicate the highest pressure encountered for this protocol or theaverage pressure encountered for this protocol. The injector systeminterface screen can then suggest a pressure limit value for theoperator to input based on this historical data. Furthermore,statistical analysis of historical pressures for a protocol may be usedto identify unusual or outlying conditions for the purpose of generatingoperator warning signals.

One additional aspect of the present invention relates to a detectioncircuit that determines the fill level of a syringe. An array of sensorsis arranged along the longitudinal axis of the syringe, so that eachtransmits a signal and receives a reflected signal. Based on whichsensor detects a reflected signal, the location of a plunger disc withinthe syringe may be located. Based on this location, the fill level ofthe syringe can be determined.

A further aspect of the present invention relates to an injector havinga removable memory device for download and upload of injectorinformation, such as injector configuration information and injectorusage statistics. Injector configuration information stored on thememory device may include injection sequences or protocols that havebeen configured by an operator, allowing those protocols to be readilytransferred from one injector to another, and/or preserved as theremainder of the injector is serviced. Injector usage statistics storedon the memory device may include hours of operation, number ofinjections, pressures and flow rates achieved and protocols utilized, aswell as software updates for the injector. The memory socket may beincluded on the powerhead, or in other connected parts of the injectorsystem, such as the console or powerpack. In a related aspect, storedprotocols may be retrieved and modified by the injector prior to use,but a password may be required before permitting the overwriting of thestored protocol.

A further aspect of the present invention relates to an injectorpowerhead for injection from first and second syringes, having multiplesyringe accessory connectors, and circuitry for identifying whether anaccessory coupled to one of those connectors is associated with thefirst or second syringe, thus freeing the operator from the burden ofconnecting a syringe accessory to an appropriate one of the syringeconnectors.

It will be appreciated that principles of the present invention areapplicable to the injection of contrast media into a patient to improveCT, Angiographic, Magnetic Resonance or Ultrasound imaging, or any otherapplication involving injection of fluids using a powered, automaticinjector.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates a power injector system according to the principlesof the present invention, and FIG. 1B illustrates the components of thepowerhead of that system.

FIG. 2 illustrates an electrical block diagram view of majorsubcomponents of a powerhead of FIG. 1B.

FIG. 3 is a partially disassembled view of the injector powerhead ofFIG. 1B showing a syringe ram position detector in accordance with theprinciples of the present invention.

FIG. 4 depicts a flowchart of an exemplary algorithm for the operationof the detector of FIG. 3.

FIG. 5 schematically illustrates an alternative embodiment of a syringeram position detector.

FIG. 6 is a partially disassembled view of the injector powerhead ofFIG. 1B showing illuminated control knobs in accordance with theprinciples of the present invention.

FIG. 7 is a partially disassembled view of the injector powerhead ofFIG. 1B illustrating the use of analog Hall-effect sensors in syringefaceplate detection in accordance with the principles of the presentinvention for detecting faceplates.

FIG. 8 depicts a flowchart of an exemplary method for detectingdifferent faceplates in accordance with the principles of the presentinvention.

FIG. 9 depicts a flowchart of an exemplary method for suggestingpressure limit values for an injection protocol.

FIG. 10 is a partially disassembled view of a faceplate for the injectorpowerhead of FIG. 1B illustrating the electrical components thereinincluding the sensor arrangement to detect attributes of a syringe inaccordance with principles of the present invention.

FIGS. 11A-11C illustrate different views of a sensor arrangement todetect attributes of a syringe in accordance with the principles of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1A, an injector 20 in accordance with the presentinvention includes various functional components, such as a powerhead22, a console 24 and powerpack 26. Syringes 36 a and 36 b are mounted tothe injector 20 in faceplates 28 a and 28 b of the powerhead 22, and thevarious injector controls are used to fill the syringe with, e.g.,contrast media for a CT, Angiographic or other procedure, which media isthen injected into a subject under investigation under operator orpre-programmed control.

The injector powerhead 22 includes a hand-operated knobs 29 a and 29 bfor use in controlling the movement of the internal drive motors engagedto syringes 36 a and 36 b, and a display 30 for indicating to theoperator the current status and operating parameters of the injector.The console 24 includes a touch screen display 32 which may be used bythe operator to remotely control operation of the injector 20, and mayalso be used to specify and store programs for automatic injection bythe injector 20, which can later be automatically executed by theinjector upon initiation by the operator.

Powerhead 22 and console 24 connect through cabling (not shown) to thepowerpack 26. Powerpack 26 includes a power supply for the injector,interface circuitry for communicating between the console 24 andpowerhead 22, and further circuitry permitting connection of theinjector 20 to remote units such as remote consoles, remote hand or footcontrol switches, or other original equipment manufacturer (OEM) remotecontrol connections allowing, for example, the operation of injector 20to be synchronized with the x-ray exposure of an imaging system.

Powerhead 22 is mounted to a wheeled stand 35, which includes a supportarm for supporting powerhead 22 for easy positioning of powerhead 22 inthe vicinity of the examination subject. Console 24 and powerpack 26 maybe placed on a table or mounted on an electronics rack in an examinationroom. Other installations are also contemplated however; for example,powerhead 22 may be supported by a ceiling, floor or wall mountedsupport arm.

Referring to FIG. 1B, details of the powerhead 22 can be seen. In FIG.1B, faceplates 28 a and 28 b have been removed, illustrating details ofthe mountings 40 a and 40 b for the faceplates. Two different faceplatesare shown in FIG. 1B. Faceplate 28 a is designed for mounting a 125 mlsyringe, and uses mechanical structures similar to those disclosed inU.S. patent application Ser. No. 10/211,726, which is herebyincorporated by reference herein in its entirety. These structuresinclude movable arms 32 which rotate into and out of engagement with thecylindrical body of the syringe to engage the syringe. The syringe isinstalled perpendicular to its axis to engage a button on the rearwardface of the syringe with a jaw on the end of the drive ram, as shown inthe above-referenced patent application. Faceplate 28 b is designed formounting a 200 ml front-loading syringe, and uses mechanical structuressimilar to those illustrated in U.S. Pat. No. 5,300,031, which is herebyincorporated by reference herein in its entirety. These structuresinclude a rotating cam, rotatable via an externally-extending arm 34 tocause translation of the faceplate 28 b relative to the mounting 40 b.The rotating cam further includes engaging keys that mate to slots on arearward end of syringe 36 b so that rotation of the syringe is linkedto rotation of the cam and translation of the faceplate. The translationof faceplate 28 b relative to mounting 40 b causes a button on arearward face of the plunger in syringe 36 b to translate into and outof engagement with a jaw on the end of the drive ram, as shown in U.S.Pat. No. 5,300,031.

The circuitry internal to powerhead 22 includes, in the area ofmountings 40 a and 40 b, Hall effect sensors for detecting magnets inthe corresponding faceplate. Specifically, there are Hall effect sensorson the circuit board internal to injector powerhead 22 at each ofpositions 70 a/70 b, 71 a/71 b and 72 a/72 b. These sensors detect thepresence or absence of a magnet in the faceplate adjacent to positions70 a/70 b, 71 a/71 b and 72 a/72 b. The sensors at positions 71 a/71 band 72 a/72 b are used to identify the faceplate mounted to powerhead22, that is, the presence or absence of a magnet in a faceplatecorresponding to these locations identifies the faceplate type and thusthe syringe size being used on that side of the injector. The sensors atpositions 70 a/70 b have an alternative purpose of identifying whetherthe faceplate is closed or open. Mountings 40 a and 40 b include, atlocations 70 a and 70 b, magnetic conductors for carrying magnetic fluxto a sensor on an internal circuit board, as discussed further belowwith reference to FIG. 7. The faceplates 28 a and 28 b each include amagnet in the movable mounting structures, that is, faceplate 28 aincludes a magnet within one of the movable arms 32, and faceplate 28 bincludes a magnet within the internal rotating cam coupled to arm 34.This magnet is positioned so that when the syringe and faceplate areengaged for injection, the magnet aligns with the magnetic conductor atlocation 70 a/70 b, triggering the sensor internal to powerhead 22.Because the movable structures in the faceplates are not as close tomountings 40 a and 40 b as magnets at locations 71 a/71 b and 72 a/72 b,and for this reason a magnetic conductor is included at locations 70a/70 b to ensure flux is channeled to the sensors internal to powerhead22.

Mountings 40 a and 40 b further include a magnetic conductor 78 a and 78b, useable to identify whether a faceplate has been connected to the Aor B side of the injector powerhead, as elaborated below. The magneticconductors 78 a and 78 b carry flux from magnets internal to thefaceplate. These magnets have opposite polarities and/or only oneconductor 78 a/78 b contains a magnet, so that the positioning of afaceplate on the A or B side of the injector may be distinguished by asensor in faceplates with appropriate sensing electronics, such as the125 ml faceplate 28 a discussed below.

Faceplate 28 a notably includes a cradle housing 76 within which thesyringe 36 a is installed. Cradle housing 76 provides mechanical supportfor syringe 36 a and may further house sensors such as are discussed indetail below with reference to FIGS. 10 and 11A through 11C.

Although the powerhead 22 discussed herein is a dual head injector,embodiments of the present invention explicitly contemplated single headinjectors as well.

Referring to FIG. 2, the powerhead includes a circuit board 160including a microprocessor to perform communications with the powerpack26 (FIG. 1). A suitable microprocessor is the Motorola/FreescaleMCF5282, which is a “Coldfire” family microprocessor suitable forembedded applications. The circuit board generates displays on display30, receives and forwards touch information from the interface display30, controls the motor drives and receives feedback informationregarding those motor drives, and controls illumination of the manualknobs 29 a and 29 b mounted on the rear of the powerhead.

The motors 98 a and 98 b are coupled to gear boxes 164 a and 164 b whichtranslate rotary motion of the motor to linear translation of theplunger. One suitable motor is a Brushless DC Motor part number N2341manufactured by Pittman of 343 Godshall Drive, Harleysville, Pa. Therotation of each motor is detected by optical encoders 166 a and 166 b(encoders 166 a and 166 b essentially comprise a pinwheel which rotatesbetween a light source and a light detector to produce electricalpulses). Encoders 166 a and 166 b send electrical pulses to circuitboard 160, which relays them to powerpack 26, allowing CPU 52 on thepowerpack to monitor movement of the motor. The motors 98 a/98 b furtherprovide three phase signals indicative of the phases of excitation ofthe stator, which are also received and monitored by circuit board 160to verify the operation of the motor and provide verification of motorrotation as detected by the encoder 166 a and 166 b.

FIG. 2 illustrates the control electronics utilized in faceplatescoupled to the injector powerhead 22. Specifically, each faceplateincludes various electrical elements, connectable to circuit board 160via a four wire connector jack 167 a/167 b including four lines 170a/170 b, 172 a/172 b, 181 a/181 b and 182 a/182 b.

As presently contemplated, each of the various types of faceplatesincludes a heater blanket or heating element. In a relatively simplefaceplate such as the faceplate for 200 ml syringes as is shown at 28 bin FIG. 1B, the faceplate electronics comprise the heater blanket 176 b(which may be a film resistive element or other electrical heatingdevice connected between lines 170 b and 172 b), and temperature sensorssuch as thermistors 178 b thermally coupled thereto and connected tolines 181 b and 182 b for detecting the syringe temperature. In arelatively complex faceplate such as the faceplate for a 125 ml syringesas is shown at 28 a in FIG. 1B, the faceplate electronics compriseheater elements 176 a (which may be high temperature resistors mountedon a circuit board 1102 internal to faceplate 28 a), a temperaturesensor integrated circuit 179 a, and also additional sensor electronics,as elaborated below.

Circuit board 160 includes pulse width modulation generating circuits168 a/168 b which generate a pulse-width modulated signals on lines 170a/170 b relative to ground on lines 172 a/172 b, to heat the faceplateheating element 176 a/176 b to a controlled temperature. The temperatureof the heater 176 a/176 b is detected by a temperature sensing circuitto provide controlled feedback of the pulse width modulation fromcircuit 168 a/168 b.

In a 200 ml faceplate, as presently contemplated, temperature sensing isprovided by a temperature sensing circuit 179 a/179 b, which is coupledto lines 181 b and 182 b, and measures the current through or voltagedrop across thermistors 178 b in the 200 ml faceplate, relative toground on line 172 b, to detect the temperature of the syringe. Thesensed temperature is converted to a digital value within circuit 179a/179 b in circuit board 160, and the result is used to control thepulse width modulated signal on line 170 b.

In a 125 ml faceplate, as presently contemplated, temperature sensing isprovided by temperature sensing electronics 178 a included on a circuitboard 1102 and thermally coupled to the syringe in the faceplate.Detected temperature information is conveyed from circuit board 1102 tomain circuit board 160 using a two-wire I²C interface over lines 181 aand 182 a. Within circuit board 160, the I²C signal is coupled to an I²Cinterface circuit 184 which receives digital communications oftemperature readings, and delivers these to the microprocessor oncircuit board 160 to control the pulse width modulated output of theconnected circuit 168.

Circuit board 1102 draws power from a power rectification circuit 180that is coupled to the pulse width modulated signal on lines 170 a/172 athat also drive resistive heater(s) 176 a. Using this power, circuitboard 1102 detects temperature as noted above, and further uses sensors1110 and 1112, the function of which is elaborated below, to detect theplunger position of the syringe and syringe fill condition, and providethat information to the microprocessor on main circuit board 160 via theI²C interface.

It will be noted that the circuitry on main circuit board 160 is adaptedto permit either a 125 ml or a 200 ml faceplate, or potentially othertypes of faceplates with other control electronics, to be selectablyconnected to either or both of the interface jacks 167 a/167 b. Notably,switches 183 a/183 b are interposed between lines 181 a/181 b and 182a/182 b and the I²C interfaces 184 a/184 b and temperature circuits 179a/179 b, thus permitting the selection by circuit board 160 of theappropriate connections for lines 181 a/181 b and 182 a/182 b based uponthe type of faceplate connected to jack 167 a and jack 167 b.

The methodology used by the microprocessor in circuit board 160 todetect and control the type of faceplate connected to jack 167 a,involves regularly setting a switches 183 a to connect lines 181 a and182 a to the corresponding I²C interface 184 a to determine if an I²Cconnection can be made. If so, then operation proceeds using lines 181 aand 182 a as an I²C connection, as with a 125 ml faceplate. If noconnection can be made, then operation proceeds by connecting lines 181a and 182 a via switches 183 a to the corresponding temperature circuit179 a, to determine if there is a return current through those linesindicative of thermistors coupled to those lines. If so, then operationproceeds using lines 181 a and 182 a for temperature sensing as with a200 ml faceplate. If no return current is detected, then it can bedetermined that no connection has been made to a faceplate on the A sideof the injector, and an appropriate error signal generated. A similarmethodology is used with lines 181 b and 182 b, switches 183 b, I²Cinterface 184 b and temperature circuit 179 b to determine and controlthe type of faceplate connected to jack 167 b.

The control circuit 160 and faceplates are further adapted so that theoperator may connect the faceplate on either the A or B side to eitherof connector jacks 167 a and 167 b without hindering operation of theinjector. Specifically, as noted above, the injector 22 mounting areas40 a and 40 b include magnetic indicators 78 a and 78 b which producedistinguishable magnetic signatures on the A and B side of the injector,such as the via the presence of a magnet in one side and the absence ofa magnet on the other, or magnets of opposite North-South orientationson the respective A and B sides. A Hall effect sensor 174 on circuitboard in the 125 ml faceplate 28 a detects the magnetic flux from themagnetic indicator 78 a when the faceplate is mounted on the injector,and delivers a signal to the faceplate electronics 1102. This signal isused to determine the I²C address at which those electronics 1102 willcommunicate over lines 181 a and 182 a. As a consequence, when the I²Cinterface circuits 184 a/184 b attempt to establish an I²C connectionover lines 181 a/181 b and 182 a/182 b, the address at which theconnection is established determines whether the faceplate is on the Aor B side of the injector, thus informing the microprocessor in circuitboard 160 where the faceplate is located, so that the microprocessor maythereafter proceed appropriately in controlling injection on theidentified side of the injector. This permits the microprocessor tocontrol the injector powerhead 22 appropriately when two faceplates ofthe same type (e.g., 125 ml type) are placed on the A and B sides of theinjector, and relieves the technician using the injector of anyrequirement to ensure that a faceplate's connection cord is connected toa particular one of the connector jacks 167 a and 167 b.

In one embodiment, circuit board 160 may include or be connected to aremovable memory card socket 204 for connection to a removable memorycard 206. Various available memory card technologies may be used forsocket 204 and card 206, such as Memory Stick™ or Secure DigitalMultimedia Memory Card (SD/MMC), as is conventionally used on digitalcameras and portable computers and personal digital assistants. Theremovable memory device may be used to download and upload of variousinjector information, such as injector configuration information andinjector usage statistics.

Injector configuration information stored on the memory device mayinclude injection sequences or protocols that have been configured by anoperator, allowing those protocols to be readily transferred from oneinjector to another. Typically the programming of an injection protocolinvolves the configuration of multiple steps each involving a flow rateand time or volume, as well as potentially various inject or scan delaytimes, pressure limits, a protocol name, and other parameters. Adifficulty with injectors known in the prior art is that such datacannot be readily migrated from one injector to another, withoutreprogramming the second injector manually. When an injector is replacedas part of service, the stored protocols are lost, which is potentiallya substantial source of frustration. Furthermore, in a hospitalenvironment having multiple injectors, technicians wishing to use aprotocol across multiple injectors would like to do so withoutreprogramming each of the injectors manually. A removable memorypermitting upload and download of such protocol information can be usedin either situation, thus dramatically simplifying the process ofmigrating protocols from one injector to another.

A further difficult with known injectors providing for stored protocolsis that those protocols are difficult to manage effectively, becausethey are subject to change by technicians. For example, in the hospitalenvironment noted above, technicians wishing to use a protocolrepeatedly on an injector or multiple injectors may be required not onlyto create the protocol(s) but to monitor the stored protocol(s) toensure it/they have not been changed by other technicians. This problemis particularly acute where one technician uses the protocol created byanother as a “starting point” for an injection having slightly differentparameters. In such a situation, there is a temptation for the secondtechnician to modify the previously stored protocol entered by the firsttechnician, and save those changes, overwriting the previously storedprotocol.

It has been proposed, e.g., in U.S. Patent Publication 2004/0064041,page 31, to provide a “protocol lock”, which may be based upon apassword, to prevent editing of a protocol. As described in thatpublication, the protocol lock must be deactivated prior to implementingany changes to a protocol. This solution avoids the scenario describedabove. However, an outright lock of any editing of a protocol, has thedisadvantage of preventing technicians from using a protocol created byanother as a “starting point”, even for one ad hoc use of the injector.

According to principles of the present invention, protocol storage ismanaged in an improved manner, as follows. A stored protocol may beassociated with a password to prevent unauthorized modification of thatstored protocol; however, the association of the password will onlyblock storage of changes, and not use or modification in general.Without entering the password, it will still be possible to retrieve andmodify of the parameters of the protocol for the purpose of an ad hocinjection; changes cannot, however, be saved overwriting the storedprotocol without providing a password. In the absence of the password,however, the injector may provide a facility to store the changedprotocol with a new name, if there is memory space available.

Furthermore, injector statistics may be uploaded from or downloaded to aremovable memory as well, for example, as the remainder of the injectoris serviced. Injector usage statistics that can be stored in theinjector and moved to the memory device may include hours of operation,number of injections, pressures and flow rates achieved and protocolsutilized. The collection of such statistics from an injector facilitatesservice and also aids in evaluation of injection needs for futuremarketing, and thus the ability to move these statistics to a removablememory will advance these objectives.

Circuit board 160 also detects the output of the Hall effect sensorsmounted on the circuit board adjacent the faceplate mounting, which areidentified at 56 a/56 b and 58 a/58 b on FIG. 2. Further detailsregarding the use of the sensors are provided below with reference toFIGS. 7-8.

In addition to the optical encoders 166 a and 166 b monitoring theposition of the syringe ram as it moves, it is also useful to know theabsolute position of the ram such as when the powerhead is powered onand off, for example. Previous approaches used linear potentiometers tomonitor the position of the syringe ram. Then, as the injector wasoperated, the potentiometer moved as the ram moved. For example, alinear-movement potentiometer would move along with a portion of theram; whereas a rotating potentiometer would rotate with the ball screw.With either type of potentiometer, a physical linkage between the ramand the potentiometer was needed.

FIGS. 2 and 3 illustrate an alternative and improved approach that doesnot require contact with the ram in order to detect the absoluteposition of the syringe ram 308 and, also, detects this position uponpowering up without the need to return to a “home” position.

The mechanism includes a two-pole magnet 306 a/306 b on each ram, aseries of analog (or linear) Hall effect sensors 312-1 a/312-1 b, 312-2a/312-2 b, 312-3 a/312-3 b for each faceplate, and control electronicson a circuit board 160. The magnet 306 a/306 b on each ram isadvantageously as small as feasible with its poles on the longest axis.In operation, the magnet 306 a/306 b is placed on the ball screw nut andthe ram attachment area. Hall-Effect sensors 312-1 a/312-1 b, 312-2a/312-2 b, 312-3 a/312-3 b are placed nearby on circuit board 160 alongthe path the nut 304 a/304 b travels, as best seen in FIG. 3 (showingnut 304 b, magnet 306 b and sensors 312-1 b, 312-2 b and 312-3 b). Theclearance distance between each magnet 306 and the sensors 312 is maderelatively small to ensure good magnetic detection, e.g., about 0.125inches. The number of Hall effect sensors to use is dependent on thetotal distance the ram 308 a/308 b moves, the length, L, of the magnet306 a/306 b, and the desired number of locations at which absoluteposition sensing is desired. While the present implementation utilizesthree sensors 312-1 a/312-1 b, 312-2 a/312-2 b, 312-3 a/312-3 b for eachram, embodiments of the present invention contemplate using as few asone sensor and more sensors than three as well.

Control electronics such as a microcontroller or microprocessorcommunicate with the sensors 312-1 a/312-1 b, 312-2 a/312-2 b, 312-3a/312-3 b in order to provide analysis of the signals from the sensors.Such control circuitry would preferably include non-volatile, andvolatile, memory, analog-to-digital converters (ADCs), and various inputand output circuitry as would be found on the main circuit board 160(FIG. 2).

FIG. 4 depicts a flowchart of one exemplary algorithm for utilizing theencoder 166 of FIG. 2 in conjunction with magnetic positioning sensors.In accordance with this method, in step 402, the “home” position of theram 308 is stored in microprocessor's memory along with the signalsreceived from the Hall-Effect sensors 312-1 a/312-1 b, 312-2 a/312-2 b,312-3 a/312-3 b in that position. Preferably, the analog signals fromthe Hall effect sensors are converted using an analog to digitalconverter (ADC) into appropriate signals for the microprocessor.Calibration of the sensors is continued in step 404 by storing a numberof different entries that associate a particular set of sensor readingswith a known position of the ram, including an end position. Duringoperation of the injector during a sequence, the microprocessor mayreceive an indication of the Hall-Effect sensors, in step 406, and use alook-up operation, in step 408, to determine the absolute position ofthe syringe ram. This operation may involve performing interpolationbetween two known sensor states and their corresponding ram positions,to approximate the ram position from the sensor signals being received.Thus, the information stored in the microprocessor's memory permitsidentifying the stroke limit positions of the syringe ram and basicposition information even if the ram is not returned to the “home”position after power is restored.

It will be noted that in the embodiment illustrated in FIG. 3, sensors312-2 b and 312-3 b are spaced widely apart, limiting the collection ofabsolute position information when the ram magnet 306 b is between thesesensors. This has not been found to be a source of difficulty as typicalinjector usage has been found to involve bringing the ram to one end ofthe stroke or another on a fairly regular basis, at which times anabsolute position may be determined with minimal interpolation error.Between such events the incremental position tracking using encoders 166a/166 b and motor phase signals from motors 98 a/98 b has been found tobe sufficiently accurate.

In an advantageous alternative embodiment, these potential limitationsof the embodiment of FIG. 3 can be removed, and the sensors arrangedsuch that the magnet 306 is always within sensing distance of twosensors (which necessarily limits the distance between sensors). Becausethe center of the magnet 306 has the same detectable flux density of nomagnet, if only one sensor were used to detect the magnet and the magnetstopped centered over that sensor, then no absolute position could bedetermined. Thus, in one particular arrangement, the magnet 306 issensed by at least two sensors as the center of the magnet passes overone of the sensors. There is preferably some overlap in the detectionregions of the sensors as well to ensure that the magnet is reliably andaccurately sensed. In such an embodiment, the magnet 304 has a length Land each sensor has an overlap length Y. The distance between twoadjacent sensors, then, is selected to be L-Y. With this spacingcriteria established, the total stroke length, D, of the injector can beused to determine the number of sensors, n. In particular, D=n*(L−Y).The vertical distance, H, between the magnet 306 and the hall sensors312-1 a/312-1 b, 312-2 a/312-2 b, 312-3 a/312-3 b is dependent on thestrength of the magnet 306 as well as the sensitivity of the sensors312. Using readily available magnets and sensors, this height wouldtypically be around 0.125 inches; however, other distances arecontemplated by the present invention as well.

FIG. 5 depicts an alternative apparatus for determining the absoluteposition of a syringe ram 308 without requiring contact potentiometersas utilized in previous position monitoring circuits. A reflectivesurface 502 is attached to the nut 304 of the ram 308 such that aradiation source 504 may transmit radiation to the surface 502 anddetect reflection therefrom. While the transmitter/detector device 504of the figure is labeled as “optical”, radiation energy outside of thevisible spectrum is explicitly contemplated within the scope of thepresent invention. One exemplary optical distance measuring device 504,that may be mounted on a circuit board 510, is manufactured by SharpElectronics as part number GP2D120. This particular optical device emitsinfrared radiation from an LED and senses the amount of light returnedafter it bounces off the reflector. The amount of light returned isproportional to the distance between the device and the reflector. Thus,within the device 504, the returned light is converted into an analogvoltage that indicates the distance of the reflective surface. An ADC,such as that found on the main circuit board 160 (FIG. 2) can be used toconvert this analog voltage into a digital signal used by amicroprocessor to calculate the absolute position of the syringe ram308. Similar to the method used in the algorithm of FIG. 4, a look uptable could be used to store an associated pairs of voltage levels andencoded positions. As a result, the absolute position of the ram 308 maybe determined by searching through the look-up table using a detectvoltage level from the device 504.

Conventional power injectors would preferably use an optical device 504that can detect distances from a range of approximately 1 cm to 30 cm.However, one of ordinary skill would recognize that a device other thatthe one identified above, or a specially designed discrete circuit, maybe utilized to customize the range of distances that could be detected.

Automatic or power injectors as described herein automatically move aram syringe so that contrast media or other fluids may fill a syringe orbe expelled from a syringe. While such operation simplifies a number oftasks for operators, there are some instances in which an operator maywant to manually control the movement of the syringe ram. Some injectorconsoles and powerheads provide push-buttons or similar mechanisms tomove the syringe ram in one direction or the other, while other consolesand powerheads additionally provide a knob that a operator may rotate toeffect movement of the syringe ram. A control bar/lever has also beenused.

Operators running power injector equipment often exit the scanner roomto avoid exposure to X-rays and other potentially harmful conditionswithin the scanner room. In such instances, the operator typicallymonitors the patient and the injector from a remotely located controlroom. As the injector carries out an injection protocol, the LEDs ordisplay on the injector will changed according to the steps of theprotocol and, also, the console typically includes a visual display thatis updated as the protocol progresses. The indicators on the injector,however, are not directly connected with the operating mechanism of theinjector, and furthermore, are not readily visible from a distance. Thisis a limitation of known injectors that is addressed by the injectordescribed herein.

FIG. 6 depicts the internal structures of the dual head injectorpowerhead 22 of the preceding figures, and the two separate manualcontrol knobs 29 a and 29 b. According to the principles of the presentinvention, the manual actuation knobs 29 a and 29 b of the injectorpowerhead 22 are utilized to provide visual feedback to an operator thatdirectly indicates the operating characteristics of the syringe ram. Themanual knob is directly coupled to the drive screw, sometimes throughgears, and is usually used to manually purge air from the system. In thecase of a multiple-headed injector, each drive system has its ownseparate manual knob 29 a and 29 b that can be used to precisely expelfluid into, or withdraw fluid from, a patient. Because the knob 29 a and29 b is connected to the ram and rotates at the same time the ram isinjecting fluid into a patient, the rotation of the knob 29 a and 29 bduring automatic injections provides direct feedback to the operatorabout the operation of the ram. For example, the rotation of the knobindicates movement of the ram as well as its relative speed. In oneexemplary embodiment, the knobs 29 a and 29 b are illuminated so thattheir rotation can be observed easily from a distance and in low lightconditions.

One or more LEDs 607 are used as a light source for lighting the insideof a knob. These LED's are electrically coupled to the circuit board 160as shown in FIG. 2, but reside on a separate circuit board 604 adjacentto the knobs 29 a and 29 b. As illustrated in detail in FIG. 6, theknobs 29 a and 29 b include opaque regions 702 and transparent ortranslucent regions 704 spaced around their periphery. The opaqueregions preferably are made of a relatively high-friction, soft feelmaterial to provide an appealing and functionally effective tactilesurface. One suitable material is commercially available under the nameSantoprene. The longitudinal striping of the opaque and transparent ortranslucent regions causes light to be emitted from some portions of theknob but not from other portions. As the syringe ram moves, the operatormay directly observe the rotation of the knob along with its relativespeed from a remote location. In one exemplary embodiment, the internalstructure of the knob preferably behaves as a light pipe 605 that guidesthe light emitted from the LEDs 607 to each of the transparent regions704 of the knobs 29 a and 29 b.

Certain conventions have developed with power injectors that associatecertain colors with the status of the injector. For example, in thepast, LEDs of a particular color were illuminated to indicate whetherthe injector was enabled, not enabled, injecting, paused,pressure-limiting, etc. The LEDs 607 depicted in FIG. 6 may be used tomaintain these conventions as well. Multi-color LEDs, therefore, may beused so that the knob 29 a/29 b is not simply illuminated but isilluminated in a color corresponding to the status of the injector.

FIG. 7 depicts a cut-away view of the portion 40 b of the powerhead 22where a faceplate 28 b mounts, showing the proximity of Hall effectsensors 56 b and 58 b to the mounting 40 b. As noted above, thepowerhead has removable faceplates 28 a and 28 b (FIG. 1), and differentfaceplates having differently-sized apertures are used to permit thepowerhead 20 to accept differently-sized syringes. For example, onefaceplate may be sized for use with low capacity syringes, whereasanother is sized for use with larger capacity syringes. Pre-filledsyringes may have different sizes or dimensions than syringes which arepurchased empty. Different faceplates 28 are needed to accommodate thesedifferent syringe sizes. Although the faceplates need not be removed toreplace the syringe, they may be removed to use different syringe sizes.It is necessary for the control circuitry on circuit board 160 to beable to detect which faceplate is installed on powerhead 22. Differentsyringe types may have differing lengths, in which case powerhead 22must be able to compensate for the length variations when determiningthe end-of-travel position of the plunger drive ram and when computingthe volume of fluid in the syringe. Similarly, syringes of differentdiameters will produce different flow rates for the same rate of travelof the plunger drive ram; the control circuitry must compensate for thiswhen converting a requested flow rate into movement of the plunger driveram. Furthermore, pre-fill syringes require a different filling sequencethan syringes that are sold empty, and the injector may implement suchdifferent sequences when a faceplate used with pre-filled syringes isinstalled.

For identification purposes, each different faceplate 28 has a uniquecombination of permanent magnets installed therein, in registration withsensors inside the injector, such as at locations 71 a/71 b in the frontsurface of the drive housing, and/or with a magnetic conductor leadingto a sensor, such as at the locations 70 a/70 b. Different embodimentsof the present invention contemplate different numbers of faceplatemagnets and different numbers of corresponding sensors 56 and 58.

To detect the number and positioning of permanent magnets in thefaceplate, the circuit board 160 of the powerhead 22 includes associatedHall effect sensors 56 a/56 b and 58 a/58 b for each magnet that may bepresent in a faceplate. These sensors 56/58 are positioned near an edgeof circuit board 160. Typically, the housing 69 of the powerhead 22 ismanufactured of a non-magnetic material such as Aluminum. Accordingly,magnetic fields produced by permanent magnets may penetrate to the Halleffect sensors so that the presence or absence of permanent magnets in afaceplate 28 can be detected remotely from the faceplate 28 by detectorson circuit board 160.

Digital Hall effect sensors have been used in past power injectorsystems to detect the presence of an injector faceplate. Such a magneticsensor, however, has a switching threshold that is set at the time ofmanufacture and is unchangeable. Thus, to detect a magnet, apredetermined minimum amount of flux must be transmitted from the magnetto the sensor. In the manufacturing process of powerhead injectors,there is enough variation from unit to unit that problems exist withdigital Hall-effect sensors reliably and accurately detecting thepresence or absence of magnets on different faceplates. One solution tothis problem is to utilize magnetic conductors which deliver flux to thesensor, as is done at locations 70 a/70 b, the use of which as disclosedin U.S. Pat. No. 5,868,710, which is commonly assigned herewith, and ishereby incorporated herein in its entirety. However, magnetic conductorsincrease manufacturing cost and complexity. Thus, in accordance with theprinciples of the present invention, the magnetic sensors 56/58 of FIG.7 are selected to be analog Hall-effect sensors instead of thetraditional digital Hall-effect sensors.

Sensors 56 a and 56 b detect whether the faceplate is open (by detectinga magnet adjacent to location 70 a/70 b on FIG. 1B), and if so, circuitboard 160 sends a message to powerpack 26 which prevents any furtherinjection procedures until the faceplate is closed. A magnetic conductoris used at location 70 a/70 b due to the likelihood that the magnetcarried by movable portions of the faceplate is likely not to beimmediately adjacent to the rearwardmost surface of the faceplate 28.

Sensors 58 a and 58 b, which are positioned on the circuit board 160 inopposition to locations 71 a/71 b and 72 a/72 b, detect the size of thefaceplate in use. For example, one faceplate, when mounted, may containa magnet at location 71 and no magnet at location 72, whereas adifferent faceplate may omit the magnet at location 71 and contain amagnet at location 72. Furthermore, sensors 56 a and 56 b may alsodetect the North-South polarity of a magnet for further discriminationof faceplates, so that a faceplate containing a magnet at location 71with the North pole facing the injector, can be distinguished from afaceplate containing a magnet at location 71 with the South pole facingthe injector. By detecting the North or South orientation of a magnet,as well as the absence of a magnet, three conditions in each oflocations 71 and 72 may be identified. This permits eight possiblecombinations of magnets to identify faceplates (each faceplate mustinclude at least one magnet to permit the injector to identify when nofaceplate is mounted). Furthermore, it is within the scope of thepresent invention to potentially permit the use of opposite polaritiesin the magnet at location 70 a/70 b, so that sensor 58 a/58 b not onlyidentifies whether the faceplate is open, but also determines polarityof the magnet at location 70 a/70 b to be used in identifying thefaceplate. If the North-South polarity detected by sensor 58 a/58 b isincluded in the variables identifying a faceplate, the number ofpossible combinations of magnets to identify faceplates may be increasedto sixteen.

Thus, the circuit board can determine which faceplate has been installedon the A and B side of the injector by determining which of the sensors58 a or sensors 58 b has been triggered, and potentially from thepolarity detected by sensor 56 a or 56 b. This information is alsoforwarded to a CPU in the powerpack so that CPU may compensate for thedifferent syringe sizes when controlling the motor 98 a and 98 b.

An advantageous algorithm for utilizing analog Hall-effect sensors infaceplate identification is provided in FIG. 8. According to thisalgorithm, a faceplate is attached, in step 902, and then, in step 904,signal levels from the analog Hall-effect sensors are acquired. In oneadvantageous embodiment, the sensor level readings are acquired with thefaceplate attached and another level reading is acquired with thefaceplate detached. A threshold value is then determined for each sensorto be approximately halfway between the two level readings. In step 906,this threshold is stored along with a faceplate identifier. Accordingly,during operation of the injector system, the analog Hall-effect sensorscan be read by the control circuitry to get a reading that is comparedto the stored thresholds. Based on this comparison, the faceplate canmore accurately be identified. In other words, the analog Hall-effectsensors, are calibrated for each faceplate and, thus, take into accountvariations in sensor manufacture, magnet strength, and other variablefactors. In certain embodiments, the signals from the sensors areobtained in such a manner that transient signal levels while thefaceplate is being positioned on the powerhead are ignored.

As discussed briefly earlier, power injector systems often includeautomatic protocols that can be selected from a menu screen. An operatorwill select information about a protocol and then modify certainparameters, if needed, to customize the protocol for each situation.Then, the powerhead can be set in an automatic operating mode thatallows the protocol to be performed substantially automatically.

Many power injector systems have a pressure limit feature that serves asa safety feature with respect to proper protocol setup and flowrestriction setup. If an operator programmed a flow rate unintentionallytoo high for a particular fluid path setup, the fluid pressure mayincrease to an unacceptable level. In other cases, the programmed flowmay be properly set but a fluid path blockage may increase the fluidpressure to an unacceptable level. In either instance, the pressurelimit feature of the software is activated and takes control of theflow-rate to lower the fluid path pressure to ensure it does not exceeda predetermined amount.

Embodiments of the present invention implement the exemplary algorithmof FIG. 9 to increase the accuracy of the pressure limit setting inputby operators. By ensuring that an appropriate pressure limit value isentered by an operator, a number of advantages are provided. Too low ofa pressure limit may unnecessarily interrupt a protocol and require theoperator to manually perform a number of functions or to manuallyaddress various alarms and warnings. If the pressure limit is set toohigh, the injector may not react to a problem until the pressureincreases past an excessively high pressure.

In accordance with the algorithm of FIG. 9, the power injector performsa variety of stored protocols, in step 1002. During the performance ofthese protocols, historical data is collected and stored, in step 1004,relating to the fluid pressures that were achieved during the protocol.The data that is collected can be statistically analyzed to determineaverage pressures, highest achieved pressures, statistically significantvariations of pressure, standard deviations of achieved pressures, etc.

When an operator retrieves a protocol from memory to perform, thesoftware of the powerhead allows the operator to input a pressure limitvalue, in step 1006. However, rather than simply relying on theoperator's knowledge or experience, the statistical information storedin memory is used to display, in step 1008, a suggestion to the user forwhat an appropriate fluid limit value would be. The suggested value maybe the average fluid pressure, for that protocol, the highest pressureachieved for that protocol, or some fixed percentage above those values.One of ordinary skill will appreciate the many different suggestedvalues can be provided to an operator based on the historical datawithout departing form the scope of the present invention.

Based on the suggestion, the operator may input a pressure limit valuefor a protocol, in step 1010. Alternatively, the suggested value may beautomatically made a default value that the operator merely confirms asthe selected value. Furthermore, regardless of the operator's selectedpressure limit, the injector may utilize pressures achieved in previousexecutions of a protocol to determine thresholds for generating warningsof overpressure, or to abort an injection. For example, one approach ofthis kind would warn the operator upon detection of a pressure that isgreater than a certain number of standard deviations from the meanpressure previously experienced for the current protocol, e.g., morethan 1.5 standard deviations above the mean, and abort an injection upondetection of a pressure that is greater than a larger number of standarddeviations from the mean pressure previously experienced, e.g., morethan 3 standard deviations above the mean.

To facilitate such statistical approaches to pressure limit calculation,the injector would need to build mean and standard deviation figuresonly from successful, normal executions of a given protocol. Thus, forexample, in the event of an overpressure condition detected by theinjector, the injector could query the operator whether an abnormalcondition such as kinked tubing caused the overpressure condition. If anabnormal condition caused the overpressure condition, then the resultingpressure data would be excluded from future statistical calculations sothat the mean and standard deviation data collected by the injector arenot skewed by abnormal data.

One useful parameter that impacts many protocols and the method in whichthey are performed is syringe capacity. In some instances, an operatormay be required to input the syringe capacity via an interface screenfor pre-filled syringes. The capacity of the syringe may differ eventhough the outer physical dimensions of the syringe remain the same. Themanual entry of this information may sometimes lead to unintentionalerrors. Accordingly, automatic detection of a pre-filled syringe and itscapacity advantageously improves the accuracy and reliability ofautomatic protocols in powered injector systems.

FIG. 10 illustrates the circuit board 1102 containing faceplateelectronics of a 125 ml faceplate as discussed above. This circuit boardutilizes sensors in an exemplary detection system, the operation ofwhich is detailed in FIGS. 11A-C. In these figures, the control board1102 houses a series of sensors 1110 and 1112. As shown and discussedwith reference to FIG. 2, this board 1102 is in communication with themain circuit board 160 (FIG. 2) that controls the operation of thepowerhead. Through this communications channel, information detected bythe sensors 1110 and 1112 may be transmitted to the main board 160 foradditional analysis or as information to use when controlling a protocolperformance.

Circuit board 1102 may be housed within a housing or other supportstructure that at least partially surrounds the circuit board 1102 andthe syringe 1104. One such housing is housing 76 shown on the powerheadof FIG. 1B. The housing 76 includes a cradle area 1120 (FIG. 11C) thatprovides the physical support of the syringe 1104 while attached to apowerhead assembly, and hold the circuit board 1102 in a fixed positionrelative to the syringe 1104.

Sensors 1110 emit radiation of a particular wavelength and detectreflection of that radiation. In particular, infrared radiation levelsare effective because the syringe 1104 is substantially transparent atthat wavelength while the plunger 1106 is non-reflective. The plungerbacker disc 1108, however, is reflective and therefore is detected byone of the sensors 1110. The plunger backer disc 1108 is locateddifferently in FIG. 11A as compared to FIG. 11B. Thus, a differentdetector 1110 will detect the presence of the disc 1108 in eachinstance. For example, the rightmost sensor 1110 detects the disc 1108for the 125 mL syringe of FIG. 11A while the left-most sensor 1110detects the disc 1108 for the 50 mL syringe of FIG. 11B. The exemplarysensor board 1102 of these figures include three sensors 1110 becauseconventionally sized syringes typically encompass the range of locationsof these three sensors. However, one of ordinary skill would recognizethat fewer or more sensors 1110 could be used without departing from thescope of the present invention.

A pair of sensors 1112 is also depicted in FIGS. 11A-C. In this pair ofsensors, one acts as a transmitter and the other as a receiver. If theoptical path between the two sensors 1112 is blocked then a differentsignal results than if it is open. For example, presence of fluid withinthe syringe 1104 will attenuate the signal between the two sensors 1112as compared to when the syringe 1104 is empty. Accordingly, the sensors1112 can be used to detect when the syringe is empty.

Ambient light may impinge on the sensors 1110 and impact the accuracy oftheir readings. Accordingly, one embodiment of the present inventioncontemplates sensors 1110 that modulate their output so that receptionof unmodulated return signals can be discarded as unwanted noise. Inaddition, or alternatively, the cradle 1120 may be constructed ofmaterial that reflects ambient light and, therefore, protects thesensors 1110 from excessive ambient light. In addition, conventionalsyringe and power injector features such as syringe heaters may beincluded such that they do not interfere with operation of the sensors1110 and 1112.

While the present invention has been illustrated by a description ofvarious embodiments and while these embodiments have been described inconsiderable detail, it is not the intention of the applicant torestrict or in any way limit the scope of the appended claims to suchdetail. Additional advantages and modifications will readily appear tothose skilled in the art. The invention in its broader aspects istherefore not limited to the specific details, representative apparatusand method, and illustrative example shown and described. Accordingly,departures may be made from such details without departing from thespirit or scope of applicant's general inventive concept.

1. A contrast media injector system comprising: a syringe ram; a drivemechanism coupled with the syringe ram and configured to move thesyringe ram; a magnet coupled with the drive mechanism; and a pluralityof magnetic sensors arranged along a path in which the magnet travels,the sensors configured to detect a presence of the magnet.
 2. The systemof claim 1, wherein the sensors are arranged such that two adjacentsensors detect the magnet.
 3. The system of claim 1, wherein the magnettravels along a path passing over the plurality of sensors.
 4. Thesystem of claim 1, wherein at least one said sensor generates a signalrepresentative of the analog magnetic field strength detected by saidsensor, the detected analog magnetic field strength being used todetermine a relative position of said magnet.
 5. The system of claim 1,further comprising a memory configured to store a respective position ofthe drive mechanism associated with a state of the sensors.
 6. Thesystem of claim 5, further comprising: a position detector configuredto: determine a detected state of the sensors; search in the memory forthe respective position associated with the detected state; anddetermine a position of the syringe ram based on the respectiveposition.
 7. The system of claim 6, wherein said sensors are analog Halleffect sensors, said memory stores a level of magnetic flux at a sensoras part of a sensor state, and said position detector compares a levelof magnetic flux from sensors to levels of magnetic flux stored in saidmemory and uses interpolation between states in said memory to determinea position of the syringe ram.
 8. The system of claim 1, wherein: eachsensor has an overlap length Y, the magnet has a length L; the syringeram travel extends over a distance D; a number of sensors issubstantially equal to D/(L−Y).
 9. The system of claim 7, wherein aspacing distance between adjacent sensors is substantially equal to(L−Y).
 10. Within a contrast media injector system, a method comprisingthe steps of: positioning a syringe ram at a plurality of differentlocations; acquiring at each location: a) a first value of the syringeram position from an encoder, and b) a second value of a magnet from aplurality of sensors configured to detect the magnet, the magnetarranged to move with the syringe ram; associating the first and secondvalues for each different location.
 11. The method of claim 10, furthercomprising the steps of: detecting a state of the sensors representingan analog amount of magnetic flux detected by the sensors; locating asecond value substantially similar to the state and identifying itsassociated first value; and determining a position of the syringe rambased on the first value.
 12. The method of claim 10, wherein thesensors are arranged such that two adjacent sensors detect the magnet.13. The method of claim 10, wherein the magnet travels along a pathadjacent to the plurality of sensors.
 14. A contrast media injectorsystem comprising: a syringe ram; a drive mechanism coupled with thesyringe ram and configured to move the syringe ram; a reflective surfacecoupled with the drive mechanism; and a optical sensor configured totransmit radiation towards the reflective surface and detect areflection therefrom.
 15. The system of claim 14, further comprising acomputing circuit configured to estimate a distance to the reflectivesurface based on the detected reflection.
 16. The system of claim 14,wherein the optical sensor has a range substantially between 1 cm and 30cm.
 17. The system of claim 14, further comprising: an encoderconfigured to determine a position of the drive mechanism; a memoryconfigured to store a respective position of the drive mechanismassociated with a detected reflection of the optical sensor.
 18. Thesystem of claim 17, further comprising: a position detector configuredto: determine a detected reflection of the optical sensor; search in thememory for the respective position associated with the detectedreflection; and determine a position of the syringe ram based on therespective position.
 19. Within a contrast media injector system, amethod comprising the steps of: positioning a syringe ram at a pluralityof different locations; acquiring at each location: a) a first value ofthe syringe ram position from an encoder, and b) a second value of alevel of a reflected signal at an optical sensor, the optical sensorconfigured to transmit radiation to a reflective surface that moves withthe syringe ram and determine an amount of reflective radiation thatreturns therefrom; associating the first and second values for eachdifferent location.
 20. The method of claim 19, further comprising thesteps of: detecting a level of radiation reflected from the reflectedsurface; locating a second value substantially similar to the level ofradiation and identifying its associated first value; and determining aposition of the syringe ram based on the first value.
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